1. Field of the Invention
The present invention relates to a graphic display method for graphically displaying the machining state of a numerical control grinding machine. More specifically, the present invention relates to such a system that is capable of displaying an image of a workpiece on a display in a manner that the displayed image of the surface being worked is changed in gradation, hue or tone in accordance with the amount of material removed from the workpiece, i.e., the amount cut or abraded away (hereinafter referred to as "cut-away amount).
2. Description of the Prior Art
In general, the function of displaying animated images of path that employs a display such as a CRT and that is combined with a numerical control machine tool which is divided into the following three functions: (1) a function for displaying the shape of a tool which is moved in accordance with a part program concerning the part into which the workpiece is to be machined; (2) a function for displaying the locus of a reference point (usually, the tip) of the tool; and (3) a function for displaying the shape of the workpiece and sequentially deleting portions of the workpiece shape which sequentially overlap with the moving tool.
FIG. 1 is a block diagram showing the arrangement of a conventional system for graphically displaying the machining state of a numerical control grinding machine.
As shown in FIG. 1, the conventional system includes an operation panel 1 having a CRT image display for displaying various configurations and for issuing operational commands, and a tape reader 2 for reading a part program described by, a tape. A program storing section 3 stores a part program read from the operation panel 1 or the tape reader 2. A program analyzing section 4 analyzes the part program stored in the program storing section 3. A function generating section 5 generates a function on the basis of the result of the analysis by the program analyzing section 4. A tool data storing section 7 stores tool profile data (TPD). A work data storing section 8 stores work profile data (WPD). A display control section 6 controls the display of images on the CRT image display on the basis of a describing command (DST) from the program analyzing section 4, an output (TPH) from the function generating section 5, the tool profile data (TPD) from the tool data storing section 7, and the work profile data (WPD) from the work data storing section 8. The system further includes a driving section 9 for driving various shafts on the basis of the output of the function generating section 5. The driving section 9 is connected to a grinder main body 10.
The conventional system operates in the following manner. A part program read from the operation panel 1 or the tape reader 2 is stored in the program storing section 3. When the execution of the program is started, in response to the describing command (DST) from the program analyzing section 4, the display control section 6 clears and initializes the CRT image display of the operation panel 1. The command indicative of the analysis by the program analyzing section 4 is also input to the function generating section 5. Subsequently, the work profile data (WPD) is read from the work data storing section 8 and it is then displayed on the CRT image display. The tool profile data (TPD) is read from the tool data storing section 7 and it is also displayed on the CRT image display with the current position of the grinding wheel serving as a reference. Thereafter, the display control section 6 operates on the basis of the output (TPH) of the function generating section 5 to move the image of the tool displayed on the CRT image display and, simultaneously, to display the path of the tool. The output (TPH) of the function generating section 5 is also received by the driving section 9 which then operates to drive various shafts.
When a conventionally known graphic display method is combined with a numerically controlled lathe in the manner shown in FIGS. 2A to 2C, the method enables machining simulation as well as graphic display during actual machining. Therefore, the method can be used advantageously to check a newly prepared part program, or to monitor the machining conditions during actual machining.
However, the following problems arise in the case where the method is applied to the machining performed by a numerical control grinder. The machining performed by a numerical control grinder greatly differs from the turning machining performed by a lathe, and it has the following features: (1) the configuration, i.e., the profile, of the workpiece is very close to that of the part which is to be finally achieved; and (2) the grinding wheel, serving as the tool, is fed at a low speed and the depth of the cut is very small.
Because of these features (1) and (2), images displayed on a display by the conventional method are such that, for instance, as shown in FIG. 3A, the path resulting from a plurality of cutting cycles virtually overlap with each other due to the small depth of the cuts. This is inconvenient, for instance, for determining the number n of the nth cutting cycle during which the condition displayed is taking place. In order to make this determination, when the image is displayed on an enlarged scale, as shown in FIG. 3B, the entire workpiece cannot be displayed at this time, making it impossible to monitor the overall machining state.
In the case of plunge cutting (not shown), since the cutting speed is low, the grinding wheel, i.e., the tool, remains substantially motionless. Particularly, when a dressing process has been inserted between a rough cutting process and a finishing process, it is impossible to determine, from the displayed path, whether the finishing is completed or not. Thus, when the path animated image display function is combined with a numerical control grinding machine, the function cannot be utilized effectively.